Aleatoric vs Improvised Music

When I was in Toronto recently recording two of my pieces I referred to a particular passage in once piece as "the aleatory section." As my collaborators were seasoned professional classical musicians I assumed they would know what I meant, and they did, roughly, but it was evident that the term "aleatory" was not one that was heard with any frequency! Sounds like a good topic for a post. Also, there was a comment on my recent post on composed and non-composed music that mentioned both aleatoric music and improvised music without distinguishing them clearly. They are different things!

As the term "improvised" music is in common use, let's take it up first. Wikipedia is usually fairly useful in providing a basic understanding of terms like this so let's consult their article on Musical Improvisation:

Musical improvisation (also known as musical extemporization) is the creative activity of immediate ("in the moment") musical composition, which combines performance with communication of emotions and instrumental technique as well as spontaneous response to other musicians.[1] Sometimes musical ideas in improvisation are spontaneous, but may be based on chord changes in classical music[1] and many other kinds of music. One definition is a "performance given extempore without planning or preparation."[2] Another definition is to "play or sing (music) extemporaneously, by inventing variations on a melody or creating new melodies, rhythms and harmonies."[3] Encyclopædia Britannica defines it as "the extemporaneous composition or free performance of a musical passage, usually in a manner conforming to certain stylistic norms but unfettered by the prescriptive features of a specific musical text. Improvisation is often done within (or based on) a pre-existing harmonic framework or chord progression. Improvisation is a major part of some types of 20th-century music, such as blues, jazz, and jazz fusion, in which instrumental performers improvise solos, melody lines and accompaniment parts.

That's the whole first paragraph. The article goes on to discuss the use of improvisation historically and in various musical genres. There are a few odd things about the above discussion, don't you think? For example, saying "the creative activity of immediate ("in the moment") musical composition, which combines performance with communication of emotions and instrumental technique as well as spontaneous response to other musicians" is a bit confusing. What does it mean to combine performance with communication of emotions and musical technique? Isn't that a category error? Performance is communication using musical technique, is it not? It's not like you add communication to performance.

Yes, improvisation can certainly encompass a spontaneous response to what the other musicians are doing, but, on the other hand, so can all performance. The first time reading, for example, a piece for violin and piano, the two musicians will not only be playing their parts in an expressive manner, they will also be responding, in an expressive manner, to the way the other musician is playing. Over time these responses will become settled, but for most creative musicians I suspect there will always be an element of expressive spontaneity, otherwise the performance would become dry and stilted, not to mention, boring.

The idea that improvisation is a performance "given extempore without planning or preparation" is a nice thought, but it almost never happens. You can have absolutely free improvisation in nearly any musical genre, but it typically happens behind closed doors, not in a performance with a listening public. Jazz, classical, rock musicians do do this sort of thing, but it is rarely done in public. It is exploratory and while it is an interesting kind of communication between musicians and can lead to original ideas, it often results in meaningless thrashing around, which is why it is not done in public much.

What is typically called "improvisation" is something rather more rehearsed. Out of practice sessions that are more or less improvised, the most expressive or useful bits are preserved and used in public performances. The musicians know, more or less, what they are going to do, individually and collectively, and there are portions that are fixed and portions that are relatively freer and everyone knows which are which. This is the typical situation with jazz and fusion.

With pop music, while there can be lots of improvisation in rehearsal, by the time of performance and recording the performance will have gelled to the point of being very largely fixed in its final form. In a lot of traditional musics, improvisation in the form of improvised variations is quite common, but it occurs within particular boundaries. In classical music, as the article notes, there were certain places, the cadenzas of concertos for example, where the individual performer was expected to improvise a solo. Sometimes this was extemporaneous, but often prepared in detail beforehand so as to avoid the tragedy of not coming up with anything good on the night!

In the Renaissance and Baroque the performance practice included the improvising of ornaments to nearly any piece. Just which and where were learned as part of one's musical education.

We have lots of examples of musicians improvising whole performances from scratch. Bach could improvise fugues and there were even contests between him and other musicians. He could improvise a fugue on a subject given to him on the spot. Beethoven could improvise whole lengthy pieces as could Mozart and a number of other musicians. As these people are primarily composers it seems that what they were doing was simply composing on the spot.

So much for improvisation, what about aleatoric music? The Latin word "alea" means "dice" so the term means music with the element of chance. Wikipedia says:

Aleatoric music is music in which some element of the composition is left to chance, and/or some primary element of a composed work's realization is left to the determination of its performer(s). The term is most often associated with procedures in which the chance element involves a relatively limited number of possibilities.

The concept is more easily understood through examples. Aleatoric music is music that is written down, unlike improvised music, but the way it is played involves chance procedures. There are examples of this in Charles Ives and Henry Cowell where the result of notated music will occur partly due to chance. There is always an indeterminate aspect to aleatory music. Three different kinds can be distinguished:

1) the use of random procedures to produce a determinate, fixed score, (2) mobile form, and (3) indeterminate notation, including graphic notation and texts

Examples of the first kind include a number of pieces by John Cage in which he used coin tosses and the I Ching to pick the notes and rhythms which he then notated in a score. The choices were random, but the score is entirely determined. Mobile form was developed by Morton Feldman, Earle Brown and Karlheinz Stockhausen and consists of a score that is precisely notated, but in which the various parts can be played in an order chosen by the performer either randomly or decided beforehand. The third kind uses a kind of notation that is intentionally vague as to pitches and rhythms so the performer is expected to intuit what would be an appropriate performance.

The type that I find the most interesting is the second one and I would like to refer to two examples. The first is perhaps the most famous instance, Klavierstück XI by Stockhausen that I posted the other day. Here is a brief excerpt with the score so you can see how it works.

Wikipedia describes the structure as follows:

Klavierstück XI consists of 19 fragments spread over a single, large page. The performer may begin with any fragment, and continue to any other, proceeding through the labyrinth until a fragment has been reached for the third time, when the performance ends. Markings for tempo, dynamics, etc. at the end of each fragment are to be applied to the next fragment.

So the order of the musical phrases is by chance as are the expressive parameters that will be applied to each phrase. This kind of structure is often called "moment form" after another piece by Stockhausen for orchestra. In my recent piece for violin and guitar I used a type of moment form in one section. The inspiration was from the Canadian composer Anthony Genge who used a version in a piece for alto flute and guitar. In my piece, this section acts as a kind of development section. All of the individual elements are taken from the rest of the conventionally notated piece. Each performer has a number of "moments" and they can be played in any order. Then they are repeated, again in any order. What moments are heard together is by chance and the performers are free to express or interpret each moment in response to what the other musician is doing. I find this a quite interesting contrast to the rest of the piece. Here is that section:

Click to enlarge

I will be putting up that whole piece, called Dark Dream, fairly soon. Right now I am working on two companion pieces to it, one called Articulated Dream and the other Dream Scherzo.